/* 连接到index.html */
*{
    font-family:-apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;

}
html,
body{
    margin: 0;
}
header{
    font-weight: 400;
    background-image: url(header.jpg);
    background-size: cover;
    background-position: center;
    padding: 60px 0;
    color: rgba(255, 255, 255, 0.8)
}
header>h1{
    font-weight: 400;
}
header>h2{
    font-weight:200;
}
header>h1,
header>h2{
    background-color: rgba(0, 0, 0, 0.4);
    font-weight:200;
    width: 30%;
    margin: 5px auto;
    text-align: center;
    background-color: rgba(0, 0, 0, 0.6);
    border-radius: 6px;
}
nav{
    text-align: center;
}
nav>ul{
    display: inline-block;
}
nav>ul li{
    list-style: none;
    float:left;
}
nav>ul li>a{
    color: #333366;
    text-decoration: none;
    display: block;
    padding: 10px;
}
body > div:nth-child(4){
    width: 40%;
    margin: 20px;
}